The present invention relates to an ink-jet printer which prints an image onto a print medium held on a rotary drum with ink ejected from a print head, and particularly, to an ink-jet printer in which ink is supplied to the print head from an ink tank which receives ink supplemented by an ink reserve bottle detachably attached thereto.
Conventionally, serial-type ink-jet printers are widely spreading. In the serial-type color ink-jet printer, a plurality of print heads and ink tanks of a relatively small capacity are integrally mounted on a carriage, and the carriage is movably attached to a guide bar extending across a paper sheet. The paper sheet is fed in a direction perpendicular to the guide bar at a constant pitch, and the carriage is moved along the guide bar each time the paper sheet is fed for one pitch. During the movement of the carriage, the print heads eject inks of different colors from the ink tanks. In the structure as described above, for example, a color image of A4 size is printed out in ten minutes. Thus, the serial-type color ink-jet printer operates at a slow print speed of 0.1 sheet per minute.
In recent years, a drum rotation type ink-jet printer capable of printing a color image at a higher speed has been suggested. This ink-jet printer includes a rotary drum rotating in one direction and a print head disposed to face a paper sheet held on the rotary drum. The print head includes a plurality of nozzle units which are arranged along the peripheral surface of the rotary drum and eject inks of different colors onto the paper sheet rotating together with the rotary drum. Each nozzle unit includes a plurality of ink-jet nozzles disposed across the paper sheet in the axial direction of the rotary drum. The color image is printed with inks ejected from the nozzle units. In this structure, the color image, for example, of A4 size can be printed out in about two or three seconds.
In this drum-rotation type ink-jet printer, a plurality of ink tanks are placed apart from the print head to store inks of different colors to be supplied to the nozzle units of the print head. Each ink tank is formed to have a structure capable of supporting an ink reserve bottle which is filled with reserve ink of a corresponding color and attached to a top portion of the ink tank. Upon attachment of the ink reserve bottle to the ink tank, ink is supplied to the ink tank from the ink reserve bottle, and the supply of ink is continued until the liquid surface of ink reaches a predetermined height in the ink tank.
However, in the drum-rotation type ink-jet printer, for example, if a user repeatedly attaches and detaches the ink reserve bottle to and from the ink tank to check the remaining amount of ink or to move the printer, ink is excessively supplied to the ink tank from the ink reserve bottle, so that the liquid surface of ink is temporarily raised beyond a predetermined height. The liquid surface of the ink is returned to the predetermined height by discharging such excessive ink from the ink tank as overflow ink. If ink is thus wastefully discharged, the number of paper sheets which can be printed out is greatly reduced with respect to the capacity of ink of one ink reserve bottle.
In addition, when ink reserve bottles are attached to ink tanks of all colors corresponding to reserve inks, there is a possibility that reserve ink of an ink reserve bottle is supplied to a wrong ink tank not corresponding to the color of the reserve ink due to an attachment error of the ink reserve bottles. In this state, a proper color image cannot be obtained at the time of printing, and it is necessary to perform a cleaning for removing ink which has flowed into the print head, the ink tank, and the piping member.